WASHINGTON (AP) - The nation's regional airlines are having trouble hiring enough pilots, the government says, suggesting one reason may be that they simply don't pay enough.

A pool of qualified pilots is available, but it's unclear whether they are willing to work for low entry-level wages, the Government Accountability Office said in a report released Friday.

One key economic indicator supports the emergence of a shortage, something regional airlines have complained of and point to as a reason for limiting service to some small communities. But two other indicators suggest the opposite is true, GAO said. Also, two studies reviewed by the GAO "point to the large number of qualified pilots that exist, but may be working abroad, in the military or in another occupation, as evidence that there is adequate supply," the report said.

The U.S. airline industry will need to hire 1,900 to 4,500 new pilots annually over the next 10 years due to an expected surge in retirements of pilots reaching age 65 and increased demand for air travel, the report said.

Eleven out of 12 regional airlines failed to meet their hiring targets for entry-level pilots last year, the report said. However, no major airlines were experiencing problems finding pilots.

Regional carriers account for about half of all domestic airline flights. One big concern is that communities served only by regional airlines will see their service reduce or eliminated. Five regional airlines told GAO they are already limiting service because of a pilot shortage.

Major airlines generally pay significantly higher salaries than regional carriers and frequently hire pilots from regionals. The average starting salary for first officers, also called co-pilots, at regional airlines is $22,400 a year, according to the Air Line Pilots Association.

Earlier this month, Wyoming-based Great Lakes Airlines ended service in a handful of small towns, citing a dearth of qualified pilots. The pilots association says Great Lakes pays newly hired first officers $16,500 a year.

"Data indicate that a large pool of qualified pilots exists relative to the projected demand, but whether such pilots are willing or available to work at wages being offered is unknown," the report said. And, the size of the pilot pool has remained steady since 2000, the report said.

There are currently 66,000 pilots working for U.S. airlines, but there are 109,465 currently active pilots with a first-class medical certificate who are licensed to fly airline passengers, the report said. An additional 100,000-plus pilots with commercial licenses might at some point choose to pursue an airline career, the report said

The unemployment rate for professional pilots is very low, only 2.7 percent. That would normally indicate a shortage, but that may not be the case, GAO said. Average professional pilot salaries went down 9.5 percent from 2000 to 2012, while the number of pilots employed went up 12 percent. Both trends are inconsistent with a shortage, the report said.

At the same time, pilot qualifications have been ramped up. Both captains and first officers need at least 1,500 hours of flying experience, although there are some exceptions. First officers used to need just 250 hours.

In a statement, the trade group for regional airlines blamed that rule for the pilot shortage and called on Congress to address it. "Its impact has proven more immediate and significant than analysts predicted," said Roger Cohen, president of the Regional Airline Association.

The new regulations stem from an aviation safety law Congress passed more than three years ago following the 2009 crash of a regional airliner near Buffalo, N.Y., that was blamed on pilot error. All 49 people on board and a man on the ground were killed. An investigation revealed that the first officer had been paid only about $16,000 the previous year, her first year at the airline. The captain was earning about $63,000. The Continental Connection flight was operated by the now-defunct regional carrier Colgan Air Inc.

The National Transportation Safety Board concluded that both pilots were suffering from fatigue, although the board stopped short of citing fatigue as a contributor to the crash. Neither pilot had slept in a bed the night prior to the fatal flight. The first officer, who lived at home with her parents, commuted across the country overnight in a jump seat in order to make the fatal flight.

Afterwards, some lawmakers questioned whether the pilots could afford hotel rooms on their salaries and said raising the qualifications for entry-level pilots would force airlines to pay more for greater experience.

So far, that doesn't appear to be happening. The average new pilot at 14 regional airlines is paid about $24 per hour for the first year of employment, GAO said. Hourly wages increase for the second year on the job for first officers to about $30. The average hourly pay for first officers at a major carrier is $48.

Classroom work and flight training in a 4-year program to qualify for commercial flying can cost well in excess of $100,000. Pilot schools GAO interviewed reported fewer students entering their programs because of the disparity between high education costs and low entry-level pay at regional airlines.

"People aren't going to work for $22,000 again, and the reason they're not going to do it is they spend $100,000 or so to get their certification, and you can't live on that amount of money, pay your student loans off and function," said Lee Moak, president of the Air Line Pilots Association.

Some regional airlines have offered new first officers signing bonuses or tuition reimbursement to attract more pilots, the report said.